It is well known that, upon color development of a silver halide color photographic light-sensitive material, an oxidation product of an aromatic primary amine color developing agent reacts with a coupler to produce indophenol, indoaniline, indamine, azomethine, phenoxazine, phenazine or a like dye to thereby form a dye image.
Couplers which can be used for formation of magenta dye images include 5-pyrazolone, cyanoacetophenone, indazolone, pyrazolobenzimidazole and pyrazolotriazole couplers.
Among them, magenta couplers that have hitherto been widely employed and undergone investigations are 5-pyrazolone couplers. It is known that dye images formed by 5-pyrazolone couplers have superior fastness to heat and light but contain a yellow component which shows unnecessary absorption at about 430 nm causing color turbidity.
In order to reduce the yellow component, there have conventionally been proposed coupler skeletons for formation of magenta dye images, such as a pyrazolobenzimidazole skeleton as described in British Patent 1,047,612, an indazolone skeleton as described in U.S. Pat. No. 3,770,447 and a pyrazolotriazole as described in U.S. Pat. No. 3,725,067.
However, magenta couplers disclosed in these patents are still unsatisfactory for reasons that: they fail to provide satisfactory magenta dye images when dispersed in hydrophilic protective colloids, e.g., gelatin, and mixed with a silver halide emulsion; they have low solubility in high boiling organic solvents; they are difficult to synthesize; or they exhibit only relatively low coupling activity when processed with an ordinary developing solution.
The present inventors had previously developed pyrazolo-azole magenta couplers including imidazo[1,2-b]pyrazoles, pyrazolo[1,5-b][1,2,4]triazoles, pyrazolo[1,5-d]tetrazoles, pyrazolo[1,5-d]benzimidazoles, and pyrazolopyrazoles which are free from the above described disadvantages.
It was noted, however, that axomethine dyes formed by these pyrazolo-azole magenta couplers show relatively low fastness to light, heat or moisture, and also conventionally employed general dye image stabilizing agents, such as alkyl-substituted hydroquinones, cannot sufficiently prevent discoloration of these dye images.